Monday, April 29, 2013
Exhibit Hall
This work investigated the rheological characteristics of steam exploded (17 kgf, 205 oC, 20 min.) and hydrothermal-pretreated (195 oC, 10 min., 200 rpm, 1:10 m/v) sugarcane bagasse (SCB) slurries during hydrolysis experiments. Compositional analyses of the samples were made in all steps. Experiments were carried out with 10% of solid loading (m/v) in 0.05 M sodium citrate buffer, pH 4.8, 250 rpm, at 50°C. A commercial cellulolytic enzyme preparation (Cellic CTec-2, Novozymes) with 10 FPU/g of dry pretreated-SCB was used. Throughout the experiments samples were periodically withdrawn for glucose analysis and assessment of the rheology. A Brookfield Digital Rheometer (model LVDV-III, USA), equipped with a vane spindle (SC4-31) and controlled by a program was used. For all tests, apparent viscosity, speed, torque, shear stress and shear rate data were collected. Measurements were made at 50oC as a function of shear rate (3.4-85.0 s-1). Density of the steam exploded and hydrothermal pretreated SCB was determined by picnometry (1.02 and 1.03 g×cm-3, respectively). Data showed that apparent viscosity of the slurries was dependent on the shear rate. A drop in slurry viscosity was observed during the first 8h of the hydrolysis reaction for pretreated SCB. The apparent viscosity approached to 0.060 Pa×s (hydrothermal) and 0.030 Pa×s (steam exploded) for 40 s-1shear rate. Shear stress versus shear rate flow data were fitted to the exponential models. Conversion of cellulose to glucose was 56% and 51%, respectively, for steam exploded and hydrothermal-pretreated SCB in 48 h.
Acknowledgments: Bioen-FAPESP and CAPES for financial support.